[FFmpeg-devel] [PATCH] fftools/cmdutils.c: Add cmd line option to override detection of cpu count

[Thilo Borgmann]

Am 04.07.21 um 14:31 schrieb Thilo Borgmann:
> Hi,
> 
>>>> add an option to override auto-detection of cpu count. Defaults to auto-detection, of course.
>>>>
>>>> -Thilo
>>>>
>>>
>>>>
>>>>  doc/fftools-common-opts.texi |  7 +++++++
>>>>  fftools/cmdutils.c           | 27 +++++++++++++++++++++++++++
>>>>  fftools/cmdutils.h           |  7 +++++++
>>>>  libavutil/cpu.c              | 14 ++++++++++++++
>>>>  libavutil/cpu.h              |  6 ++++++
>>>
>>> The changes to libavutil and cmdutils should be in separate patches; and
>>> of course the commit message should mention that you are changing
>>> libavutil -- I would have nearly missed this patch (given that I don't
>>> pay much attention to fftools in general).
>>>
>>>>
>>>> diff --git a/libavutil/cpu.c b/libavutil/cpu.c
>>>> index 52f6b9a3bf..ccd5b5adac 100644
>>>> --- a/libavutil/cpu.c
>>>> +++ b/libavutil/cpu.c
>>>
>>> 52f6b9a3bf is the state of cpu.c after
>>> e387fcd01cb84d9493f3b96158addd2a85f086c6. This is completely outdated.
>>
>> Yes, messed up branches for the patch, thx!
>>
>>
>>>>
>>>> @@ -306,14 +307,27 @@ int av_cpu_count(void)
>>>>      nb_cpus = sysinfo.dwNumberOfProcessors;
>>>>  #endif
>>>>  
>>>> +    int count = atomic_load_explicit(&cpu_count, memory_order_relaxed);
>>>> +
>>>>      if (!printed) {
>>>>          av_log(NULL, AV_LOG_DEBUG, "detected %d logical cores\n", nb_cpus);
>>>> +        if (count > 0) {
>>>> +            av_log(NULL, AV_LOG_DEBUG, "overriding to %d logical cores\n", count);
>>>> +        }
>>>>          printed = 1;
>>>>      }
>>>>  
>>>> +    if (count > 0) {
>>>> +        nb_cpus = count;
>>>> +    }
>>>> +
>>>>      return nb_cpus;
>>>>  }
>>>>  
>>> In particular, this hunk doesn't apply to git master at all any more
>>> (did I already mention that cpu.c only has 245 lines atm, not >300?).
>>> And the declaration of count would lead to a statement-after-declaration
>>> warning.
>>
>> Done locally to apply to today's HEAD. I think I'll wait with sending both patches once we decided on atomic loads in "[PATCH] Stop using _explicit atomic operations where not necessary.".
> 
> Discussion on atomic loads appear to have stalled mid-June... If there are no hard feeling, I'll push this version soon as the explicit (or not) loads can then be changed later.

Pushed, thanks!

-Thilo